Basestation for cellular communications system

ABSTRACT

A basestation for a cellular communications system includes back-to-back software stacks for terminating messages from a mobile station intended for the core network, and for recreating the messages in a form suitable for transmission to the core network, and further for terminating messages from the core network intended for a mobile station, and for recreating the messages in a form suitable for transmission to the mobile station.

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 11/801,419, filed on May 8, 2007. U.S.patent application Ser. No. 11/801,419 claims priority from UnitedKingdom Patent Application No. 07 03603.1, filed on Feb. 23, 2007. Thesedocuments are hereby incorporated by reference and for all purposes.

This invention relates to a basestation for use in a cellulartelecommunications system, and in particular to a basestation for use asa femtocell basestation. A traditional cellular telecommunicationssystem includes a number of basestations, each serving a part of thetotal coverage area of the system, these areas being termed cells. Eachbasestation is connected to the core network of the system, typicallyover a wired connection. A user of a wireless communications device,located in one of these cells, is able to establish wirelesscommunications with the relevant basestation, and the traffic is passedover the wired connection to the core network, where it can be routed asrequired.

It has been suggested that, in order to increase the capacity ofcellular telecommunications systems, femtocell basestations canadditionally be provided. It has been suggested that a femtocellbasestation could be obtained by a customer of the mobile networkoperator, and located within that customer's premises, which may forexample be a home or a relatively small office. The femtocellbasestation could then be connected to the core network of the cellulartelecommunications system over the customer's existing broadbandinternet connection. In this case, a user of a suitably registeredwireless communications device (which may for example be the customer'sown conventional cellular wireless communications device), when it islocated within the relatively small coverage area of the basestation(this area being termed a femtocell), is then able to establish wirelesscommunications with the relevant femtocell basestation, and the trafficis passed over the broadband internet connection to the core network,where it can be routed as required.

It is known that, in some cases, certain operations require relativelylarge numbers of messages to be transferred between the basestation andthe core network, even in a conventional cellular communications system.In addition, in use of the femtocell basestation as described above,traffic that is intended to be uploaded from the registered wirelesscommunications device to a device that is connected to the internet, oris intended to be downloaded to the registered wireless communicationsdevice from a device that is connected to the internet, is passedthrough the core network of the cellular communications system, placingan additional burden on the core network.

According to a first aspect of the present invention, there is provideda basestation, having software that allows the basestation to terminateand/or interrogate messages sent from a mobile device that are intendedfor the network, and/or allows the basestation to terminate and/orinterrogate messages sent from the network that are intended for themobile device.

This has the advantage that, in some situations, the number of messagestransferred between the basestation and the network can be reduced.Further, the basestation operator can provide additional services to theuser.

For a better understanding of the present invention, and to show how itmay be put into effect, reference will now be made, by way of example,to the accompanying drawings, in which:

FIG. 1 is a block schematic diagram of a part of a cellular wirelesscommunications network.

FIG. 2 shows the functional architecture of a part of the networkillustrated in FIG. 1.

FIG. 3 is a protocol stack diagram, illustrating software operating onnodes in the part of the network shown in FIG. 2 in an embodiment of theinvention.

FIG. 4 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 2 in anembodiment of the invention.

FIG. 5 shows the functional architecture of a part of the networkillustrated in FIG. 1, in an alternative embodiment.

FIG. 6 is a protocol stack diagram, illustrating software operating onnodes in the part of the network shown in FIG. 5 in an embodiment of theinvention.

FIG. 7 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 5 in anembodiment of the invention.

FIG. 8 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 5 in anembodiment of the invention.

FIG. 9 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 5 in anembodiment of the invention.

FIG. 10 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 5 in anembodiment of the invention.

FIG. 11 is a further protocol stack diagram, illustrating softwareoperating on nodes in the part of the network shown in FIG. 5 in anembodiment of the invention.

FIG. 12 illustrates a method in accordance with an aspect of theinvention.

FIG. 1 illustrates a part of a cellular wireless communications networkin accordance with an aspect of the present invention. Specifically,FIG. 1 shows a core network (CN) 10 and a radio network (RN) 12 of acellular wireless communications network. These are generallyconventional, and are illustrated and described herein only to thelimited extent necessary for an understanding of the present invention.

Thus, the core network 10 has connections into the Public SwitchedTelephone Network (PSTN) (not shown) and into a packet data network, forexample the internet 14. The radio network 12 may include, for example,a GSM radio network and/or a UMTS radio network, which are thengenerally conventional. As shown in FIG. 1, the radio network 12 has abasestation (BS) 16 connected thereto. As will be recognized by theperson skilled in the art, a typical radio network 12 will have manysuch basestations connected thereto. These basestations provide coverageover respective geographic areas, or cells, such that a service isavailable to subscribers. Often, there is a group of basestations thattogether provide coverage to the whole of the intended service area,while other basestations provide additional coverage to smaller areaswithin that intended service area, in particular to smaller areas wherethere is expected to be more demand for the service. The cells served bythe basestations of the first group are then referred to as macrocells,while the smaller areas served by the additional basestations arereferred to as microcells.

FIG. 1 also shows an additional basestation 18 that can be used toprovide coverage over a very small area, for example within a singlehome or office building. This is referred to as a femtocell basestation(FBS). The femtocell basestation 18 is connected into the mobile networkoperator's core network 10 over the internet 14, by means of thecustomer's existing broadband internet connection 20. Thus, a user of aconventional mobile phone 22 can establish a connection through thefemtocell basestation 18 with another device, in the same way that anyother mobile phone can establish a connection through one of the otherbasestations of the mobile network operator's network, such as thebasestation 16.

As mentioned above, the macrocell basestations provide coverage to thewhole of the intended service area including the location of thefemtocell basestation 18 and the location of the mobile phone 22 whileit is in the coverage area of the femtocell basestation 18. However, thenetwork is configured such that, when a mobile device that is allowed tobe registered with the femtocell basestation 18 is within the coveragearea of the femtocell basestation 18, then it will preferentiallyestablish a connection with the femtocell basestation 18 rather thanwith the macrolayer basestation 16.

FIG. 2 shows the functional architecture of a part of the networkillustrated in FIG. 1. Specifically, the mobile phone, or user equipment(UE), 22 is shown, having a connection into the femtocell basestation(FBS) 18 over a Uu radio interface. Other devices can also be used toconnect to the FBS 18, such as a POTS or SIP phone 26, which can connectover a POTS or SIP interface, as appropriate, or a PC 28, which can forexample connect over IP, or over USB, or over WiFi, or over an Ethernetconnection.

The FBS 18 includes a USIM 30, which can take the form of a SIM card asis conventional, or can contain the required data in any removable ornon-removable module. The USIM 30 allows the FBS 18 to identify itselfto the mobile network operator's core network as if it were itself amobile device, and provides suitable authorization and encryptionfunctionality.

The FBS 18 has a connection over the generic IP access network 14 to theinternet 31.

In this case, the FBS 18 uses the UMA (Unlicensed Mobile Access)protocol for backhaul, and has a Up′ interface over the generic IPaccess network 14 to a 3G L-GANC (Generic Access Network Controller) 32.

The FBS 18 is also able to establish a Zz interface over the generic IPaccess network 14, through a security gateway 34 in the Generic AccessNetwork Controller 32 to a management system (MS) 36. The managementsystem 36 is operated by the mobile network operator, and supports theoperation of the femtocell basestations, such as the FBS 18, within thenetwork.

The 3G L-GANC (Generic Access Network Controller) 32 is then connectedto the core network 10 of the mobile network operator. The network maybe the Home Public Land Mobile Network (HPLMN) or the Visited PublicLand Mobile Network (VPLMN) defined in the 3G specifications. In thisillustrated case, the network includes both a Mobile Switching Center(MSC) 38 for circuit switched data, to which the GANC 32 may establish alu-CS interface, and a Serving GPRS Support Node (SGSN) 40 for packetswitched data, to which the GANC 32 may establish a lu-PS interface.

FIG. 3 illustrates the circuit switched domain control plane protocolstacks that are provided in the various network nodes, namely the UE 22,the FBS 18, nodes of the IP access network 14, the 3G L-GANC 32 and theMSC 38.

As is well known, the WCDMA protocol structure is divided verticallyinto an Access Stratum (AS) and a Non-Access Stratum (NAS). The AccessStratum (AS) includes the Layer 1 (L1) protocol, the Media AccessControl (MAC) protocol, the Radio Link Control (RLC) protocol, and theRadio Resource Control (RRC) protocol. It can be seen that these areterminated in the FBS 18, and interworked into the relevant UMA protocollayers for transmission over the IP access network 14 to the GANC 32,where they are terminated again, and interworked into the relevantprotocols for transmission to the MSC 38.

By contrast, the UE 22 and the MSC 38 would be able to communicatedirectly with each other using the Non-Access Stratum (NAS) protocols,which may include the Call Control (CC) protocol, the SupplementaryServices (SS) protocol, the Short Message Service (SMS) protocol, theMobility Management (MM) protocol, and the Connection Management (CM)protocol, for example.

However, in accordance with an aspect of the present invention, the FBS18 includes software 42 for terminating messages from the UE 22 in theprotocols of the Non-Access Stratum that are intended for the MSC 38,and also includes software 44 for terminating messages from the MSC 38in the protocols of the Non-Access Stratum that are intended for the UE22. The FBS 18 also includes intelligence function (IF) software 46 forproviding an interworking or relay function between the software 42 andthe software 44.

Thus, in this embodiment of the invention, and others, the software inthe FBS 18 includes software for interworking between the wirelesscommunications over the Uu interface on the one hand and thecommunications using the UMA protocol with the 3G L-GANC on the otherhand.

However, the software in the FBS 18 also includes back-to-back NASsoftware stacks. These stacks allow messages in the NAS protocol layers,that have been sent from the UE and would conventionally be expected tobe received in the MSC, to be terminated in the FBS 18. Messages canthen be recreated for onward transmission to the MSC, either in the sameform or with modification of one or more parameter value, or themessages can instead be handled in a different way, for example bytransmitting a message over the internet without passing through theMSC. Similarly, the software in the FBS 18 also allows messages in theNAS protocol layers, that have been sent from the MSC and wouldconventionally be expected to be received in the UE, to be terminated inthe FBS 18. Messages can then be recreated for onward transmission tothe UE, either in the same form or with modification of one or moreparameter value, or the messages can instead be handled in a differentway.

The operation of the software 42, 44, 46 in the FBS 18 will be describedin more detail below.

FIG. 4 illustrates the packet switched domain control plane protocolstacks that are provided in the various network nodes, namely the UE 22,the FBS 18, nodes of the IP access network 14, the 3G L-GANC 32 and theSGSN 40.

As before, the protocol structure is divided vertically into an AccessStratum (AS) and a Non-Access Stratum (NAS), and the Access Stratum (AS)includes the Layer 1 (L1) protocol, the Media Access Control (MAC)protocol, the Radio Link Control (RLC) protocol, and the Radio ResourceControl (RRC) protocol. It can be seen that these are terminated in theFBS 18, and interworked into the relevant UMA protocol layers fortransmission over the IP access network 14 to the GANC 32, where theyare terminated again, and interworked into the relevant protocols fortransmission to the SGSN 40.

By contrast, the UE 22 and the SGSN 40 would be able to communicatedirectly with each other using the Non-Access Stratum (NAS) protocols,which may include the GPRS Mobility Management (GMM) protocol, theSession Management (SM) protocol, and the Short Message Service (SMS)protocol, for example.

However, in accordance with an aspect of the present invention, the FBS18 includes software 48 for terminating messages from the UE 22 in theprotocols of the Non-Access Stratum that are intended for the SGSN 40,and also includes software 50 for terminating messages from the SGSN 40in the protocols of the Non-Access Stratum that are intended for the UE22. The FBS 18 also includes intelligence function (IF) software 52 forproviding an interworking or relay function between the software 48 andthe software 50.

Thus, in these embodiments, the FBS 18 supports the relevant protocolsto make the UE 22 believe that it is working into a 3G UMTS network.Towards the network, the FBS 18 supports the UMA protocols to make theGANC 32 believe that it is communicating with a UMA client and to makethe MSC 38 (or SGSN 40) believe that it is communicating with a 3G UE.The intelligence function 46, 52 can be programmed to pass informationbetween the 3G and UMA stacks transparently e.g. relaying so that therelevant 3G UE protocols (NAS) communicate transparently through the FBSwith the 3G MSC. Alternatively the intelligence function 46, 52 can beprogrammed to terminate all or of some of the protocols as appropriate.The terminated protocols are then interworked. It is also possible toprogram the intelligence function 46, 52 to interrogate the protocolsthen relaying some parts and interworking other of the same protocol.

FIG. 5 shows the functional architecture of a part of the networkillustrated in FIG. 1, in an alternative embodiment. Specifically, amobile phone, or user equipment (UE), 122 is shown, having a connectioninto the femtocell basestation (FBS) 118 over a Uu radio interface.Other devices can also be used to connect to the FBS 118, such as a POTSor SIP phone 126, which can connect over a POTS or SIP interface, asappropriate, or a PC 128, which can connect over IP, or over USB, orover an Ethernet connection.

The FBS 118 includes a USIM 130, which can take the form of a SIM cardas is conventional, or can contain the required data in any removable ornon-removable module. The USIM 130 allows the FBS 118 to identify itselfto the mobile network operator's core network as if it were itself amobile device, and provides suitable authorization and encryptionfunctionality.

The FBS 118 has a connection over the generic IP access network 114 tothe internet 131.

In this case, the FBS 118 has a slightly modified lub interface,referred to as an lub′ interface, a 3G RNC (Radio Network Controller)132.

The FBS 118 is also able to establish a Zz interface over the generic IPaccess network 114, through a security gateway 134 in the Radio NetworkController 132 to a management system (MS) 136. The management system136 is operated by the mobile network operator, and supports theoperation of the femtocell basestations, such as the FBS 118, within thenetwork.

The Radio Network Controller 132 is then connected to the core network110 of the mobile network operator. The network may be the Home PublicLand Mobile Network (HPLMN) or the Visited Public Land Mobile Network(VPLMN) defined in the 3G specifications. In this illustrated case, thenetwork includes both a Mobile Switching Center (MSC) 138 for circuitswitched data, to which the RNC 132 may establish a lu-CS interface, anda Serving GPRS Support Node (SGSN) 140 for packet switched data, towhich the RNC 32 may establish a lu-PS interface.

FIG. 6 illustrates the lub control plane protocol architecture, showingthe protocol stacks that are provided in the FBS 118, nodes of the IPaccess network 114, and the RNC 132. Specifically, the FBS 118 includessoftware 142 for terminating Radio Resource Control (RRC) messages fromthe UE 122 that are intended for the RNC 132, and also includes software144 for terminating RRC messages from the RNC 132 that are intended forthe UE 122. The FBS 118 also includes intelligence function (IF)software 146 for providing an interworking or relay function between thesoftware 142 and the software 144.

FIG. 7 illustrates the lu-CS control plane protocol architecture,showing the protocol stacks that are provided in the various networknodes, namely the UE 122, the FBS 118, nodes of the IP access network114, the RNC 132 and the MSC 138.

As discussed above, the WCDMA protocol structure is divided verticallyinto an Access Stratum (AS) and a Non-Access Stratum (NAS). The AccessStratum (AS) includes the Layer 1 (L1) protocol, the Media AccessControl (MAC) protocol, the Radio Link Control (RLC) protocol, and theRadio Resource Control (RRC) protocol. It can be seen that these areterminated in the FBS 118, and transmitted over the IP access network114 to the RNC 132, where they are terminated again, and interworkedinto the relevant protocols for transmission to the MSC 138.

By contrast, the UE 122 and the MSC 138 would be able to communicatedirectly with each other using the Non-Access Stratum (NAS) protocols,which may include the Call Control (CC) protocol, the SupplementaryServices (SS) protocol, the Short Message Service (SMS) protocol, theMobility Management (MM) protocol, and the Connection Management (CM)protocol, for example.

However, in accordance with an aspect of the present invention, the FBS118 includes software 152 for terminating messages from the UE 122 inthe protocols of the Non-Access Stratum that are intended for the MSC138, and also includes software 154 for terminating messages from theMSC 138 in the protocols of the Non-Access Stratum that are intended forthe UE 122. The FBS 118 also includes intelligence function (IF)software 156 for providing an interworking or relay function between thesoftware 152 and the software 154.

The operation of the software 152, 154, 156 in the FBS 118 will bedescribed in more detail below.

FIG. 8 illustrates the lu-CS control plane protocol architecture,showing the protocol stacks that are provided in the various networknodes, namely the UE 122, the FBS 118, nodes of the IP access network114, the RNC 132 and the MSC 138.

The UE 122 and the RNC 132 would be able to communicate directly witheach other using the Media Access Control (MAC) protocol and the RadioLink Control (RLC) protocol. However, in accordance with an aspect ofthe present invention, the FBS 118 includes software 162 for terminatingmessages from the UE 122 in the MAC and RLC protocols that are intendedfor the RNC 132, and also includes software 164 for terminating messagesfrom the RNC 132 in the MAC and RLC protocols that are intended for theUE 122. The FBS 118 also includes intelligence function (IF) software166 for providing an interworking or relay function between the software162 and the software 164.

FIG. 9 illustrates the packet switched domain control plane protocolstacks that are provided in the various network nodes, namely the UE122, the FBS 118, nodes of the IP access network 114, the RNC 132 andthe SGSN 140.

As before, the protocol structure is divided vertically into an AccessStratum (AS) and a Non-Access Stratum (NAS), and the Access Stratum (AS)includes the Layer 1 (L1) protocol, the Media Access Control (MAC)protocol, the Radio Link Control (RLC) protocol, and the Radio ResourceControl (RRC) protocol. It can be seen that these are terminated in theFBS 118, and transmitted over the IP access network 114 to the RNC 132,where they are terminated again, and interworked into the relevantprotocols for transmission to the SGSN 140.

By contrast, the UE 122 and the SGSN 140 would be able to communicatedirectly with each other using the Non-Access Stratum (NAS) protocols,which may include the GPRS Mobility Management (GMM) protocol, theSession Management (SM) protocol, and the Short Message Service (SMS)protocol, for example.

However, in accordance with an aspect of the present invention, the FBS118 includes software 172 for terminating messages from the UE 122 inthe protocols of the Non-Access Stratum that are intended for the SGSN140, and also includes software 174 for terminating messages from theSGSN 140 in the protocols of the Non-Access Stratum that are intendedfor the UE 122. The FBS 118 also includes intelligence function (IF)software 176 for providing an interworking or relay function between thesoftware 172 and the software 174.

FIG. 10 illustrates the lu-PS control plane protocol architecture,showing the protocol stacks that are provided in the various networknodes, namely the UE 122, the FBS 118, nodes of the IP access network114, the RNC 132, the SGSN 140, and the GGSN (not shown in FIG. 5), towhich the SGSN 140 is connected.

The UE 122 and the RNC 132 would be able to communicate directly witheach other using the Media Access Control (MAC) protocol, the Radio LinkControl (RLC) protocol, and the Packet Data Convergence Protocol (PDCP).However, in accordance with an aspect of the present invention, the FBS118 includes software 182 for terminating messages from the UE 122 inthe MAC, RLC and PDCP protocols that are intended for the RNC 132, andalso includes software 184 for terminating messages from the RNC 132 inthe MAC, RLC and PDCP protocols that are intended for the UE 122. TheFBS 118 also includes intelligence function (IF) software 186 forproviding an interworking or relay function between the software 182 andthe software 184.

There are thus described various embodiments of the invention, in whichthe topmost protocol layers are terminated in the femtocell basestation.However, in other embodiments of the invention, less of the protocolsare terminated in the femtocell basestation, while still allowing thebasestation to perform useful functions.

For an example of this, FIG. 11 is similar to FIG. 7, but illustrates analternative form of the lu-CS control plane protocol architecture,showing the protocol stacks that are provided in the various networknodes, namely the UE 122, the FBS 118, nodes of the IP access network114, the RNC 132 and the MSC 138.

As discussed above, the WCDMA protocol structure is divided verticallyinto an Access Stratum (AS) and a Non-Access Stratum (NAS). The AccessStratum (AS) includes the Layer 1 (L1) protocol, the Media AccessControl (MAC) protocol, the Radio Link Control (RLC) protocol, and theRadio Resource Control (RRC) protocol. It can be seen that these areterminated in the FBS 118, and transmitted over the IP access network114 to the RNC 132, where they are terminated again, and interworkedinto the relevant protocols for transmission to the MSC 138.

In addition, the UE 122 and the MSC 138 communicate directly with eachother using some of the Non-Access Stratum (NAS) protocols, includingthe Call Control (CC) protocol, the Supplementary Services (SS)protocol, the Short Message Service (SMS) protocol, and parts of theMobility Management (MM) protocol.

However, in accordance with an aspect of the present invention, the FBS118 includes software 192 for terminating messages from the UE 122 in apart of the Mobility Management (MM) protocol that are intended for theMSC 138, and also includes software 194 for terminating messages fromthe MSC 138 in that part of the Mobility Management (MM) protocol thatare intended for the UE 122. The FBS 118 also includes intelligencefunction (IF) software 196 for providing an interworking or relayfunction between the software 192 and the software 194.

Terminating these messages in the part of the Mobility Management (MM)protocol allows the FBS 118 to obtain the IMSI of the UE 122. Forexample, this allows the FBS to determine which UE is attempting toregister with the FBS 118, so that registration requests by non-allowedUEs can be terminated without core network involvement. Also, thisallows for data from the UE 122 to be transferred over the internet 131rather than over the core network, if this is more convenient.

Thus, in these embodiments, the FBS 118 supports the relevant protocolsto make the UE 122 believe that it is working into a 3G UMTS network.Towards the network, the FBS 118 supports the relevant protocols to makethe RNC 132 and the MSC 138 (or SGSN 140) believe that they arecommunicating with a 3G UE. The intelligence function 146, 156, 166,176, 186, 196 can be programmed to pass information between the stackstransparently e.g. relaying so that the relevant 3G UE protocols (NAS)communicate transparently through the FBS with the 3G MSC. Alternativelythe intelligence function can be programmed to terminate all or of someof the protocols as appropriate. The terminated protocols are theninterworked. It is also possible to program the intelligence function tointerrogate the protocols, then relaying some parts and interworkingother of the same protocol.

It will be apparent that the same principle can be applied in othersituations. For example, the femtocell basestation can be connected intoa 2G core network (for example based on GPRS), rather than a 3G corenetwork, as described here. In this case, the software in the femtocellbasestation also provides interworking between a 2G core network and a3G air-interface.

The operation of the intelligence function (IF) software and theillustrated protocol stacks in the FBS 18 will be described in moredetail below. In the following description, reference will be made tothe embodiment of FIG. 3 above, and thus reference will be made to theUE 22, the FBS 18, and its software 42, 44, 46. However, thesereferences are simply for illustration, and it should be appreciatedthat the same description applies to the other illustrated embodiments,and to other embodiments within the scope of the invention.

As described above, software 42 is provided in the FBS 18 forterminating messages from the UE 22 in the protocols of the Non-AccessStratum that are intended for the relevant node of the core network 10.A signalling connection is therefore established between the UE 22 andthe FBS 18. This allows the UE 22 to communicate through the FBS 18without needing to adapt its transmissions in any way, compared to thesituation in which it communicates through any other basestation.

Similarly, software 44 is provided in the FBS 18 for terminatingmessages from the relevant node of the core network 10 in the protocolsof the Non-Access Stratum that are intended for the UE 22. A signallingconnection is therefore established between the node of the core network10 and the FBS 18. This allows the core network node to communicatethrough the FBS 18 without needing to adapt its transmissions in anyway, compared to the situation in which it communicates with a UEthrough any other basestation.

As described above, the FBS 18 also includes software 46 for providingan interworking or relay function between the software 42 and thesoftware 44. This software can determine how to handle the receivedmessages, terminated by the software 42 or the software 44, based on themessage type and/or the message content.

For example, the software 46 can be such that some messages areeffectively simply retransmitted in the same form.

In other cases, the software 46 can be such that certain messages neednot be retransmitted. For example, wireless communication protocolstypically allow the UE to request retransmission of messages that it wasnot able to receive correctly. In a conventional network, such messagesare transmitted from the UE to the core network node and cause themessage to be retransmitted from the core network node, and thereforeuse core network resources. In this case, such messages can beterminated by the software 42 and read by the software 46, and theretransmission can take place from the FBS 18, without requiring anytraffic to be sent to the core network and without any use of corenetwork resources.

As another example, use of the software 46 enables Layer 3 (and above)control in the FBS 18 of all CS and PS calls.

As another example, use of the software 46 enables local registrationand call attempts to be accepted or rejected locally without having togo over to the core network. That is, local registration and callattempt messages can be terminated by the software 42, and read by thesoftware 46, which can also make a decision without requiring corenetwork involvement.

As another example, use of the software 46 enables local serviceswithout core network involvement.

As another example, use of the software 46 enables local internetoffload. That is, a message sent from the UE 22, and intended for arecipient accessible over the internet, can be terminated by thesoftware 42 and read by the software 46. The software 46 can then decideto route this message over the internet 30 directly, as illustrated inFIG. 2, without requiring core network involvement.

More generally, the software 46 may allow the FBS 18 to operate in atermination mode, in which it may terminate any layer of the protocol oneither side of the double stack interface, that is, in the software 42or the software 44, as appropriate.

To explain this, it needs to be understood that each layer of theprotocol stack has messages associated with it. These messages are onlyunderstood within the layer. Usually, the messages are point to point,which requires the protocol to be terminated in the receiving node.Termination means for instance that the node has call states, e.g. anull state waiting for an incoming SETUP message. Once received, thenode moves to a call present state. This state can notice that thetraffic channel requested in the setup message is not available. If thisis the case, it sends a RELEASE COMPLETE message and enters the nullstate. Otherwise it sends a CALL PROCEEDING message to the networkindicating the call has been accepted. Thus, when a protocol isterminated it can interact with its peer layer. Also, when the protocolis terminated, it can then interwork with other protocols. For example,a node may be provided with 3G UE CS signalling on one interface towardsone network entity, with SIP on another interface towards a differentnetwork entity. The CS protocol uses information elements IE whilst theother is text based.

In embodiments of the invention, the basestation 18 is provided withsoftware that allows it to terminate various protocol layers, asillustrated above, even where the sending node intends the messages tobe sent transparently through the basestation (for example from themobile device to the network, or from the network to the mobile device).Terminating the protocol provides more scope to add features andservices.

The basestation may then:

support relevant call states;

relay the protocol messages;

map messages to the same protocol messages;

map (interwork) protocol messages to other protocols (e.g. CS-SIP);

subsume/discard protocol messages (location updates);

convert information (e.g. converting between the cell-id and thegeographical coordinates of the cell);

provide local services (without passing on the messages, for example, tothe core network);

make decisions based on the protocol message;

initiate messages without instruction from the core network;

map between different codecs (eg AMR-G.711 PCM).

Additionally, the FBS 18 may only interrogate protocol messages, withoutsupporting call states (for example by receiving a release message thatwould take the state from answered to clear). In the case of protocolinterrogation, a decision can be made by the intelligence functionsoftware to change parts of the protocol message on the fly as it passesbetween the interfaces. No call states would be involved. Protocolinterrogation is thus essentially an intelligent relaying function,which differs from a conventional relaying function in that, althoughthe basestation merely passes the message on, it could potentiallyrecognise the message, so that, if it was a release message, it couldsubstitute another clearing cause within it.

In the interrogation mode the FBS can, depending on the protocolmessage, on either side of the dual stack interface:

relay the protocol messages;

map messages to the same protocol messages;

subsume/discard protocol messages (such as location updates);

alter information in a message (e.g. between cell-id and geographicalcoordinates).

FIG. 12 illustrates a situation where the mapping functionality is used.This situation arises from the fact that the core network may forexample allocate 10 Location Area Code (LAC) values (i.e. 1, 2, . . . ,10) and 6000 Cell-IDs (i.e. the values 1-6000) to the femtocell network(that is, a total of 60,000 unique combinations of LAC value andCell-ID). However, to provide additional flexibility in its resourceallocation, the femtocell management system may for example prefer tomaintain these 60,000, by using just 6 Cell-IDs (i.e. 1, 2, . . . , 6),but 10,000 LAC values (i.e. the values 1-10,000).

This can be achieved by mapping the LAC values and Cell-IDs in the corenetwork domain to virtual LAC values and Cell-IDs in the femtocellnetwork domain. As shown in FIG. 12, the LAC values 1, 2, . . . , 10 inthe core network domain are mapped to virtual LAC values 1-1000,1001-2000, . . . , 9001-10,000 in the femtocell network domain, whileCell-IDs 1-1000, 1001-2000, . . . , 5001-6000 in the core network domainare mapped to virtual Cell-IDs 1, 2, . . . , 6 in the femtocell networkdomain

For this scheme to work, it is necessary that LAC values and Cell-IDs inmessages sent from the core network to the mobile devices should bemapped to the appropriate virtual LAC values and Cell-IDs, and that,conversely, virtual LAC values and Cell-IDs in messages sent to the corenetwork from the mobile devices should be mapped to the appropriate LACvalues and Cell-IDs.

This is achieved in the intelligence function software by termination ofthe relevant messages, removal of the values from the sending domain,and insertion of the values from the receiving domain, followed byretransmitting the messages in the appropriate protocol.

This therefore allows the messages to be sent, and correctly received,without the sending entity needing to know that the message has beenterminated in the basestation.

The invention claimed is:
 1. A method of handling a circuit-switched orpacket-switched call in a femtocell basestation, the method comprising:receiving, at the femtocell basestation, a message from a user equipmentdevice in a protocol of the Non-Access Stratum, intended for a MobileSwitching Centre or a SGSN or GGSN in a core network of atelecommunications network; terminating the message in the protocol ofthe Non-Access Stratum; and performing local call control based on themessage, wherein the step of performing local call control comprises:having terminated the message in the protocol of the Non-Access Stratum,obtaining an IMSI of the user equipment device; determining whether theuser equipment device is allowed to register with the femtocellbasestation; and if the user equipment device is not allowed to registerwith the femtocell basestation, terminating a registration attempt.
 2. Amethod as claimed in claim 1, wherein the step of performing local callcontrol comprises performing Layer 3 control.
 3. A method as claimed inclaim 1 or claim 2, wherein the call is a circuit-switched call intendedfor the Mobile Switching Centre in the core network of thetelecommunications network and the message is a message in the CallControl protocol of the Non-Access Stratum.
 4. A method as claimed inclaim 1 or claim 2, wherein the call is a packet-switched call intendedfor the SGSN or GGSN in the core network of a telecommunications networkand the message is a message in the Session Management protocol of theNon-Access Stratum.
 5. At least one non-transitory computer readablestorage medium having computer program instructions stored thereon thatare arranged to perform the following operations in a femtocellbasestation: receive a message from a user equipment device in aprotocol of the Non-Access Stratum, intended for a Mobile SwitchingCentre or a SGSN or GGSN in a core network of a telecommunicationsnetwork; terminate the message in the protocol of the Non-AccessStratum; and perform local call control based on the message, whereinthe step of performing local call control comprises the followingoperations in the femtocell basestation: having terminated the messagein the protocol of the Non-Access Stratum, obtain an IMSI of the userequipment device; determine whether the user equipment device is allowedto register with the femtocell basestation; and if the user equipmentdevice is not allowed to register with the femtocell basestation,terminate a registration attempt.
 6. The at least one non-transitorycomputer readable storage medium as claimed in claim 5, wherein the stepof performing local call control comprises performing Layer 3 control.7. The at least one non-transitory computer readable storage medium asclaimed in claim 5 or claim 6, wherein the call is a circuit-switchedcall intended for the Mobile Switching Centre in the core network of thetelecommunications network and the message is a message in the CallControl protocol of the Non-Access Stratum.
 8. The at least onenon-transitory computer readable storage medium as claimed in claim 5 orclaim 6, wherein the call is a packet-switched call intended for theSGSN or GGSN in the core network of a telecommunications network and themessage is a message in the Session Management protocol of theNon-Access Stratum.
 9. A femtocell basestation configured to handle acall, comprising: memory, a plurality of interfaces, and one or moreprocessors, the one or more processors configured to: receive a messagefrom a user equipment device in a protocol of the Non-Access Stratum,intended for a Mobile Switching Centre or a SGSN or GGSN in a corenetwork of a telecommunications network; terminate the message in theprotocol of the Non-Access Stratum; and perform local call control basedon the message, wherein the step of performing local call controlcomprises: having terminated the message in the protocol of theNon-Access Stratum, obtaining an IMSI of the user equipment device;determining whether the user equipment device is allowed to registerwith the femtocell basestation; and if the user equipment device is notallowed to register with the femtocell basestation, terminating aregistration attempt; wherein the call is a circuit-switched callintended for the Mobile Switching Centre in the core network of thetelecommunications network, and wherein the message is a message in aCall Control protocol of the Non-Access Stratum.
 10. The femtocellbasestation as claimed in claim 9, wherein the step of performing localcall control comprises performing Layer 3 control.
 11. The femtocellbasestation as claimed in claim 9 or claim 10, wherein the call is apacket-switched call intended for the SGSN or GGSN in the core networkof a telecommunications network and the message is a message in theSession Management protocol of the Non-Access Stratum.
 12. Abasestation, for use in a mobile communications system, the basestationcomprising back-to-back software stacks, for: terminating messages in afirst protocol from a UE, determining whether one of said messages fromthe UE is a message requesting retransmission of a first message,retransmitting said first message from the basestation without sendingtraffic to the mobile network if it is determined that one of saidmessages from the UE is a message requesting retransmission of saidfirst message, determining whether said messages need to be passed tothe mobile network, and recreating messages in the first protocol foronward transmission to the mobile network only if it is determined thatthe messages need to be passed to the mobile network, thus reducing thenumber of messages passed to the mobile network; and for terminatingmessages in the first protocol from the mobile network, and recreatingmessages in the first protocol for onward transmission to the UE.
 13. Abasestation as claimed in claim 12, wherein said back-to-back softwarestacks are further adapted for determining whether said messages fromthe UE can be transmitted over the internet without passing to themobile network.
 14. At least one non-transitory computer readablestorage medium, for use in a basestation of a mobile communicationssystem, the at least one non-transitory computer readable storage mediumhaving computer program instructions stored thereon that are arranged toperform the following operations: terminate messages in a first protocolfrom a UE, determine whether said messages need to be passed to themobile network, recreate messages in the first protocol for onwardtransmission to the mobile network only if it is determined that themessages need to be passed to the mobile network, determine whether oneof said messages from the UE is a message requesting retransmission of afirst message, and retransmit said first message from the basestationwithout sending traffic to the mobile network if it is determined thatone of said messages from the UE is a message requesting retransmissionof said first message, thus reducing the number of messages passed tothe mobile network; and terminate messages in the first protocol fromthe mobile network, and recreate messages in the first protocol foronward transmission to the UE.
 15. The at least one non-transitorycomputer readable storage medium as claimed in claim 14, wherein thecomputer program instructions are further arranged to determine whethersaid messages from the UE can be transmitted over the internet withoutpassing to the mobile network.